How to Use MongoDB Transactions in Node.js?

Using MongoDB transactions in Node.js involves several steps. Transactions allow multiple operations on the database to be executed in an all-or-nothing manner, ensuring data consistency. we will learn how to use MongoDB transaction in Node.js.

Prerequisites

• MongoDB (Version 4.0 or higher Recommended)
• Replica set

Steps to Use MongoDB Transactions in Node.js

First, make sure you have the mongodb package installed. You can install it using npm:

npm install mongodb

Step 1: Connect to MongoDB

Create a MongoClient instance and connect to your MongoDB server.

const { MongoClient } = require('mongodb');
const uri = "mongodb://localhost:27017";
const client = new MongoClient(uri);

await client.connect();

Step 2: Start a Session

Start a session to use for the transaction.

const session = client.startSession();
session.startTransaction();

Step 3: Perform Operations in the Transaction

Use the session object to perform multiple operations.

const database = client.db('testdb');
const collection1 = database.collection('collection1');
const collection2 = database.collection('collection2');

try {
    await collection1.insertOne({ name: "Alice" }, { session });
    await collection2.insertOne({ name: "Bob" }, { session });

    await session.commitTransaction();
    console.log('Transaction committed.');
} catch (error) {
    await session.abortTransaction();
    console.error('Transaction aborted due to an error:', error);
} finally {
    session.endSession();
}

Step 4: Commit or Abort the Transaction

• If all operations succeed, commit the transaction.
• If any operation fails, abort the transaction.

await session.commitTransaction();

If there is an error.

await session.abortTransaction();

Step 5: End the Session

End the session after committing or aborting the transaction.

session.endSession();

Step 6: Close the MongoDB Client

Close the MongoDB client to clean up resources.

await client.close();

Example: Here is an example of using MongoDB transactions in a Node.js application.

const { MongoClient } = require("mongodb");

async function main() {
    const uri = "mongodb://localhost:27017";
    // Replace with your MongoDB connection string
    const client = new MongoClient(uri);

    try {
        await client.connect();

        const session = client.startSession();
        session.startTransaction();

        const database = client.db("testdb");
        const collection1 = database.collection("collection1");
        const collection2 = database.collection("collection2");

        try {
            await collection1.insertOne({ name: "Alice" }, { session });
            await collection2.insertOne({ name: "Bob" }, { session });

            await session.commitTransaction();
            console.log("Transaction committed.");
        } catch (error) {
            await session.abortTransaction();
            console.error("Transaction aborted due to an error:", error);
        } finally {
            session.endSession();
        }
    } finally {
        await client.close();
    }
}

main().catch(console.error);

Output: Run " node mongots.js " to see output in terminal.

Database Stores it:

Note: It is crucial to handle errors appropriately by catching exceptions and ensuring the transaction is aborted if any operation fails.